1. Field of the Invention
The field of the invention relates to an apparatus for ultrasonically cutting and sealing materials made from thermoplastic fibers.
2. Brief Description of the Prior Art
Ultrasonic cutting and sealing has been recognized as an effective means for avoiding frayed edges when cutting thermoplastic textile materials into desired shapes or sizes. U.S. Pat. No. 3,378,429 discloses an apparatus for performing this function. An ultrasonic horn is provided with a tool tip including a tapered cutting surface. As material is passed between the horn and anvil, it is compressed and sealed by the wider portion of the tapered surface and then cut by the narrower portion of this surface.
U.S. Pat. No. 3,679,526 employs a wire strip as a cutting surface. U.S. Pat. No. 3,852,144 uses a resiliently mounted cutting disk. An anvil including a knife edge portion is used in U.S. Pat. No. 4,161,420 for severing brassiere tapes. U.S. Pat. Nos. 4,025,374 and 4,227,959 relate to similar methods for cutting and sealing various materials.
Ultrasonic machinery has come into use in the bedding industry over the last several years. U.S. Pat. No. 4,234,983 concerns the manufacture of pocketed spring coils by ultrasonically welding a non-woven material after a coil spring has been inserted between plies thereof. The strings of pocketed coils may be assembled into a mattress innerspring construction in several different ways. In one method, one continuous string is maneuvered into a sinuous configuration so as to form a plurality of rows connected at the ends. Series of twines are used for connecting the rows so that they will remain in a substantially rectangular arrangement.
A square arrangement of pocketed coils within an innerspring assembly is disclosed in U.S. Pat. No. 4,234,984. A series of individual strips of coils are joined at alternative locations to arrive at this configuration. Since pocketed coil springs are generally manufactured in strings of considerable length, these strings must be cut to length wnen assembling an innersrping construction in such a manner. It is important that the springs within the end pockets remain there even after such cutting.